LEMUR MONGOZ 



39 



joint and posture discrimination. Marked prominence of the cuncus is 

 signilicant particularly of highly developed discriminative sensibility in the 

 hand. Conversely, a lack of such prominence indicates an upper extremity 





FIG. 21. DORSAL SURFACE OF BRAIN STEM, LEMUR MONGOZ. 



[Actual Length, 35 mm.] 



Key to Diagram, d. med. fis., Dorsomedian Fissure; d.m.s., Dorsomedian Sulcus; inf. coll., Inferior 

 Colliculus; SUP. CER. ped., Superior Cerebellar Peduncle; sup. coll., Superior Colliculus; tub. tr., Tuber- 

 culum Trigemini. 



and hand still mainly employed in locomotion. Of the two dorsal columns in 

 lemur, the clava and cuneus, the former seems to be structurally emphasized 

 because it represents the path of sensory conduction not only from the leg 

 but also from the important steering and balancing organ, the tail. The 

 cuneus in lemur is indicative of a forelimb as yet wholly inadequate for 

 advanced manual adaptation. 



A fairly well-defined dorsolateral sulcus extends upward upon either 

 side of the dorsomedian seam, becoming most prominent in the region between 



